1. Field of the Invention
This invention relates to a method for the preharvest control of aflatoxin in crops. This is accomplished by inoculating either the crop or the soil in which it is grown with non-aflatoxigenic strains of Aspergillus parasiticus (A. parasiticus), deposited and designated as NRRL 18786 and NRRL 18991.
2. Description of the Prior Art
Aflatoxins are potent hepatotoxic, carcinogenic compounds produced by fungi, particularly Aspergillus flavus (A. flavus) and A. parasiticus [Cast, (1989) Mycotoxins: economic and health risks. Report 116. Council for Agricultural Science and Technology). When these fungi invade and grow in agricultural commodities such as peanuts, corn, and cottonseed, the resulting contamination with the aflatoxins often makes the commodity unfit for consumption. They are a serious threat to humans and animals [Cast, Counc. Agric. Sci. Technol. Rep., Vol. 80, (1979), Ames, IA., 56 pp.]. The four naturally-occurring aflatoxins are designated B.sub.1,B.sub.2,G.sub.1, and G.sub.2 and will hereafter be collectively referred to as aflatoxin.
The United States peanut industry has identified aflatoxin contamination of peanuts as the number one problem for which a solution is needed [Consensus Report of the National Peanut Council Quality Task Force (1987) National Peanut Council].
Because peanuts are used primarily for food, strict regulatory limits for the amount of aflatoxin allowable in finished peanut products have been established. Although the U.S. Food and Drug Administration (FDA) has an action level of 20 parts per billion (ppb) of total aflatoxins in finished products, several states are considering much stricter limits for aflatoxin in food. For this reason the U.S. peanut industry has a goal to ensure the delivery of aflatoxin-free peanut products by the year 2000.
Although aflatoxin contamination of peanuts can occur during postharvest curing and storage, the most significant source of contamination is usually preharvest contamination, which occurs during periods of late-season drought stress as peanuts are maturing. The only known method for controlling preharvest aflatoxin contamination in peanuts is irrigation [Cole, R. J. (1982), Dev. Ind. Microbiol. Vol. 23, pp. 229-236; Cole, R. J., Aflatoxin Contamination of Groundnut: Proceedings of the International Workshop, Oct. 6-9, 1987, ICRISAT Center, India], an option that is unavailable to the majority of peanut growers.
It has previously been found that co-cultivation of either A. parasiticus or A. flavus with species of Penicillia reduce levels of aflatoxin production while co-cultivation with Fusaria had no such effect [Ehrlich, et al., Experientia, Vol. 41, pp. 691-693, (1985)]. These tests did not involve the use of a soil environment. Co-cultivation with A. niger completely eliminated the production of aflatoxin by a producer culture of A. flavus [Wicklow, et al., Phytopathology, Vol. 70, pp. 761-764, (1980)]. This testing was done under laboratory controlled conditions in which the food source involved sterilized corn kernels.